﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace work1
{
    class work1
    {

        public static void Main(string[] args)
        {
            double pai = 3.14f;
            double S = 0;
            double r = 0;
            Console.WriteLine("请输入圆的半径r");
            string sum = Console.ReadLine();
            r = double.Parse(sum);
            S = pai * r * r;
            Console.WriteLine("圆的面积为："+S);
            
        }

    }
}
